I cannot believe that nobody has yet mentioned Minatsuki Takami. There have been Deadman Wonderland references here and yet nobody has considered the most twisted girl I've seen in anime for a long time. Minatsuki is basically a 17 year old girl who looks sweet and innocent at first, but is actually the most manipulative, sadistic, brutal person you will ever see. She first appears in Deadman Wonderland trying to escape the prison where the series is set with the protagonist, Ganta, but fails to get away, only for it to turn out she orchestrated the whole thing simply to give Ganta an injury before their scheduled superpower fight (the Carnival Corpse) the next day. She manipulates him through the whole jailbreak attempt while staying apparently sweet and pure by 'accidentally' revealing her breasts and other parts of herself and 'accidentally' ripping her dress.
In the Carnival Corpse itself we find her power, her 'Branch of Sin', is the ability to turn her blood into whips which she uses to attack her enemies - she proceeds to not only attak her opponent, Ganta, but also her own brother when he tries to intervene, and uses her brother as a human shield against Ganta's own attacks. Throughtout this, she constantly insults both young men, and claims that clearly neither of them have "ever pelasured a woman" - she discusses this with her own brother, for crying out loud. She also turns out to be a sadist to the point where she gets off on violence, but not as tamely as you'd think - she's literally having an orgasm through the entire fight right in front of her brother and Ganta, and constantly references sex throughout her insults. Ironically, after the fight we see that she's actually very protective of herself and won't even allow any guy in the same room as her when she's getting changed, despite her otherwise provocative nature.
For losing the battle she's sentenced in the prison to have a part of her body removed (fortunately the good guys manage to influence it so she only has a haircut) - she reveals that previously she's had a kidney and half her stomach removed for losing Carnival Corpse fights. This is probably the first time, by the way, that we see any sign of humanity in her, even after she is willing to let Ganta (who only beats her by headbutting her) and her brother live following the fight. Even then she flies off the handle if she even suspects Ganta (who's interested in someone else anyway) of perving - bear in mind she's the one who was getting a literal orgasm from nearly torturing him, both physically and psychologically. She kind of joins the good guys as a minot character later, but even then everything about Minatsuki is twisted and wrong.
She became that way when her mother abandoned her during the Red Hole Incident (a massive earthquake that destroyed Tokyo) ten years earlier - her mother saved a primrose in a pot instead of her own daughter. She thus has a bizarre obsession with flowers, particularly primroses, and uses them to help manipulate people. She also murdered her own father with her Branch of Sin power, and let her brother take the blame (he didn't actually know she was responsible) - not to mention she faked an entire set of abuse instances to make sure her father and brother hated each other, and lied that her father was sexually abusing her as part of that - she was maybe 12 or 13 at the time. And since being incarcerated in Deadman Wonderland she's been subject constantly to experimentation, torture, and literal death matches almost every day, and again probably been getting a new orgasm every day from those fights. So yeah, the girl's completely messed up.
Then again, there are plenty of messed up characters in the series, and they tend to be my favourites anyway. One guy goes psycho and flips out when his assassination plan fails against the good guys, and another young girl (maybe 8 years old) slaughtered her entire kindergarten class because of her whacked out mother's teachings, got sentenced to death to be served at Deadman Wonderland, and spends her time killing the superpowered Deadmen (the good guys) with an oversized elasticated hammer. It's a crazy anime/manga, and I love it xD.
CAPTCHA: funny farm - yes, that's exactly where these people should all be... 
